Centrifugal air cleaner



Dec. l5, 1942 R. R. cREsswELJ..

CENTRIFUGAL AIR CLEANER Filed Feb. 17, 1941 Patented Dec. 15, 1942 UNITED STATES PATENT OFFICE OENTRIFUGAL AIR CLEANER Roger R. Cresswell, Minneapolis, Minn., assigner to Donaldson Company, Inc., St. Paul, Minn., a corporation of Delaware Application February 17, 1941, Serial No. 379,209

2 Claims. (Cl. 183-9'1) My invention relates to air cleaners and more particularly to air cleaners or dust collectors of the cyclone or centrifugal type, and has for its particular object the improvement of air cleaners of this type.

Air cleaners of the centrifugal or cyclone type have in long practice been found quite highly efiicient for the removal of dust and dirt from dust-laden air. Air cleaners of the oil bath or oil spray type have in long practice been found even more highly efficient than air cleaners of the centrifugal type, but an objection thereto has been that they quite rapidly accumulate dirt in the oil, which accumulation gradually decreases the eiclency of the cleaner and requires frequent recleaning ofthe oil.

In an attempt to combine the good features of both of the above noted type of air cleaners in an air cleaning apparatus, centrifugal air cleaners have been connected in tandem with oil bath or oil spray cleaners in an arrangement where the dust-laden air would first be delivered to the centrifugal cleaner and thence to the oil spray or oil bath cleaner and finally to the intake of an internal combustion engine or the like. With this tandem arrangement it was known that the centrifugal cleaner would remove from the air a major portion of the dust or dirt; and it was assumed that by thus relieving the oil cleaner from a large part of the work, that a iinal cleaning action would be more perfect, that is, that the air delivered to the intake of the engine would be cleaner or freer from dirt or dust than had hitherto been delivered from an oil bath or spray cleaner which took the dust.

laden air directly from the atmosphere. however, was not the result accomplished.

The important problem then, it seemed to me, was to obtain at least as high air cleaning eiiiciency in the tandem arrangement as was obtained in the sole use of the oil spray or bath cleaner. The advantage of this would be high efdciency and less frequent cleaning of the oil bath or vapor cleaner.

My experiments seemed to determine that the reason for hitherto failure in obtaining high emciency in the above tandem arrangement was due to the fact that in passing the dust-laden air through the centrifugal cleaner, the larger or.clotlike portions of the dust were caused to whirl and make many revolutions against and in frictional contact with the surrounding wall of the cleaner and were thereby broken up and reduced to the finest kind of dust by such grinding This,

the centrifugal cleaner to the oil spray cleaner was of such character that more of this fine impalpable dust would pass through the bath or action; and hence, that the dust delivered from oil spray and hence to the engine.

I have eifectually solved the above problem and produced a centrifugal air cleaner that will not break up or reduce the dust particles by the above noted grinding action.

My invention in what is at present. considered its preferred form is illustrated in the accompanying drawing wherein like characters indicate like parts throughout the several views.

Referring to the drawing:

Fig. 1 is a perspective view showing the parts in substantially axial vertical section; and

Fig. 2 is a horizontal section taken approximately on the line 2-2 of Fig. 1.

The numeral 5 indicates an outer shell preferably of light sheet metal, the' main body portion of which is dome-shaped and has a radially olfset portion 5a. Within the outer shell 5 isa closely perforated inner or separating shell 6 that is preferably dome-shaped and is spaced from the shell E to form a collecting chamber l. As a secondary but important feature, the top of the perforated dome-shaped separating shell 6 has a substantially ilat imperforate portion 6a,

plate 9, the inner edge of which is rigidly secured to the exterior of air outlet tube 8 at l0. This annular coupling plate 9 is formed with circumferentially spaced air passages il and with obliquely deecting blades I2.

Underlying the offset portion 5a of the outer shell 5, coupling plate 9 is likewise offset, and rigidly secured to this offset portion is a coveracting nipple I3 which may be of the character of a fruit jar cover. Detachably applied to this cover-acting nipple I3 is a secondary collecting chamber which may be and preferably is a transparent jar, such as a fruit jar, i4.

The collecting chamber 'l in this arrangement acts as the primary dust-collecting chamber, the major active portion of which is within the offset extension 5a. This offset portion of the priupward through the openings ii in the annular plate 8 and the inclined blades i2 will cause the air to partake of a spiral movement and the dust or dirt particles to be directly and immediately'thrown radially outward against the perforated surface of the separating shell 6. This direct delivery of the dust-laden air against the As has been thoroughlyfdemonstrated in practice, when this improved separator is connected to the intake of an oil bath or oil spray separator and the outlet of the latter is connected to an air intake of an internal combustion engine,

for example, the amount of dust that will reach the engine will be reduced to a very minimum.

Otherwise stated, with the vsuggested tandem' arrangement, the oil bath or oil spray separator will be rendered as efficient or more emcient than l when the air delivered to the engine is taken directly from the air through a very efficient type of oil bath or oil spray separator, and the accumulation of dust in the oil bath or oil spray said perforated separating shell is of the utmost importance. It causes the `heavier dust particles and, in fact, substantially all of the dust or dirt particles t' be immediately projected against the perforated surface, and the greater part thereof will be directly delivered through the perforations into the collecting chamber 1. If some of the particles should strike the imperforated surface of the separating shell, they would only move very slightly until they would come into and under the action of centrifugal force would be projected outward through other perforations so that all grinding action of the dust or dirt particles is nearly or quite eliminated. In this action the spherical shape of the perforated separating shell is important because it causes more direct a'nd immediate engagement ofthe dust particles with the perforated surface. 'I'he at imperforate upper portion 6a 'of the perforate dome or shell prevents the, air pressure from causing an upward draft or movement of the dust-laden air on the axis or closely on the axis of the outlet sleeve or tube 8. and in this respect it should be noted that the flat imperforate surface 6a is at least asV great and preferably of greater diameter than the diameter of the upper end of the said sleeve 8. 1

Some of the very nest dust will be carried downward and outward through the sleeve 8 commingled with the air from which the major portion of the dust and dirt has been removed. Nevertheless, with this perforate shell against which the dust-laden air is immediately and di rectly projected the amount of dust that is so ne that it swould be carried with the air outward through the sleeve 8 is reduced to a minimum. Moreover, the dust or dirt yparticles that may be designated as miniature clots will be thrown out ward through the perforated separating shell and into the collecting chamber 1 but they have been ground Vto that extremely fine character that they would be carried with the air and are so fine that they rwill more readily pass through an oil bath or especially through an oil shower. Hence, with this improved separator or air cleaner, the dust removing efiiciency of the centrifugal separator is primarily increased over the older forms of centrifugal or cyclone dust collectors air cleaner will be very slow and frequent cleaning thereof will be'made unnecessary.

The dust that passes through the perforate separating shell into the collecting chamber 1 will quite freely pass into the secondary collecting chamber Il but some thereof usually will and may accumulate in said collecting chamber 1 and especially in the laterally offset portion thereof.

The partition I8 prevents any'dust that has -once reached the collecting chamber 1 from making a complete rotation therein and ymost of such d ust will be caused to quickly stop its rotaryl movement and will be directed into the removable secondary collecting chamber i4 through the passage i5 from theV one side or the other of the said partition I6.

What I claim is:

1. In an air cleaner of the centrifugal type, an

tdownwardly substantially to the horizontal plane `of the top of said axial air outlet tube, whereby the intaken dust-laden air will be given a whirling rotation and projected directly against the perforated surface of said shell, causing much of the dust to pass directly through the perforations and into said dust collecting chamber, said domelike separating shell having an imperforate crown plate overlying the receiving end of said axial outlet tube.

2. In an air cleaner of the centrifugal type, an outer shell, a separating shell located within said outer shell and spaced therefrom to afford a dust collecting chamber, an air outlet tube extended downward from said separating shell and spaced therefrom to afford an annular air intake passage, means for setting up a whirling movement of the incoming dust-laden air, said separating shell being of 4dome-like form upwardly tapered and having closely located perforations extended downwardly substantially to the horizontal plane of vthe top of said axial air outlet tube, iwhereby the intaken dust-laden air will be given a whirling rotation and projected directly against the perforated surface of said shell, causing much of the dust to pass directly through the perfora-` 1 tions and into said dust collecting chamber, said and the character of the dust that does move l with the air to an oil bath or oil spray separator, when the outlet tube or sleeve 8 is connected to the intake of the latter, is reduced to a minimum. 

